Modern silicon-based transistors often include a high-k dielectric layer as gate dielectric. For example, a silicon-based transistor is fabricated using a complementary-metal-oxide-semiconductor (CMOS) process flow. As shown in FIG. 1, a high-k dielectric layer 102 (e.g., HfO2) is often formed on an interfacial layer 104 (e.g., SiO2) grown on a silicon substrate 106 for fabricating the transistor 100. Dipole effects often occur at the interface between the high-k dielectric layer 102 and the interfacial layer 104, as shown in FIG. 2. The interfacial layer 104 may have a larger areal density of oxygen atoms (i.e., a higher a), compared with the high-k dielectric layer 102. The difference in the areal density of oxygen atoms between the high-k dielectric layer 102 and the interfacial layer 104 is compensated by oxygen atoms transferring (e.g., in a form of O2−) from the interfacial layer 104 to the high-k dielectric layer 102, leaving behind oxygen vacancies in the interfacial layer 104 (e.g., in a form of VO2+), which results in interface dipole effects. A post-high-k annealing process is often performed to repair defects and reduce the interface dipole effects between the interfacial layer 104 and the high-k dielectric layer 102 so as to improve device performance. Usually, rapid thermal annealing (RTA) is used for the post-high-k annealing process.
Other processes may also be involved for fabricating the transistor. For example, the silicon substrate is doped (e.g., adding desired impurities into the substrate) to form junctions. Dopants introduced into the substrate are usually electrically activated, and the activation of the dopants often includes transferring the dopant atoms/molecules from interstitial positions into lattice sites of the lattice structure of the substrate.
Under certain circumstances, the fabrication process of the transistor involves microwave radiation which typically includes electromagnetic waves with wavelengths ranging from 1 m to 1 mm (corresponding to frequencies between 0.3 and 300 GHz). When microwave radiation is applied to a certain material (e.g., a dielectric material) which includes electric dipoles, the dipoles change their orientations in response to the changing electric fields of the microwave radiation and thus the material may absorb the microwave radiation to generate heat. The response of the material to the electric field of the microwave radiation can be measured using a complex permittivity, ∈(ω)*, which depends on the frequency of the electric field:∈(ω)*=∈(ω)′−i∈(ω)″=∈0(∈r(ω)′−i∈r(ω)″)  (1)where ω represents the frequency of the electric field, ∈(ω)′ represents a real component of the complex permittivity (i.e., a dielectric constant), and ∈(ω)″ represents a dielectric loss factor. In addition, ∈0 represents the permittivity of a vacuum, ∈r(ω)′ represents the relative dielectric constant, and ∈r(ω)″ represents the relative dielectric loss factor.
Whether a material can absorb the microwave radiation can be characterized using a loss tangent, tan δ:
                              tan          ⁢                                          ⁢          δ                =                                                            ɛ                ″                            ⁢                              μ                ′                                      -                                          ɛ                ′                            ⁢                              μ                ″                                                                                        ɛ                ′                            ⁢                              μ                ′                                      +                                          ɛ                ″                            ⁢                              μ                ″                                                                        (        2        )            where μ′ represents a real component of the magnetic permeability of the material, and μ″ represents a magnetic loss factor. Assuming negligible magnetic loss (i.e., μ″=0), the loss tangent of a material is expressed as follows:
                              tan          ⁢                                          ⁢          δ                =                                            ɛ              ″                                      ɛ              ′                                =                                    ɛ              r              ″                                      ɛ              r              ′                                                          (        3        )            
Materials with a low loss tangent (e.g., tan δ<0.01) allow microwaves to pass through with very little absorption. Materials with an extremely high loss tangent (e.g., tan δ>10) reflect microwaves with little absorption. Materials with an intermediate loss tangent (e.g., 10≧tan δ≧0.01) can absorb microwave radiation.